An endoprosthesis is an artificial device that is placed inside a human or animal body. An anatomical lumen is a cavity of a tubular organ such as a blood vessel. Stents are generally cylindrically shaped devices, which function to hold open and sometimes expand a segment of a blood vessel or other anatomical lumen such as urinary tracts and bile ducts. Stents are often used in the treatment of atherosclerotic stenosis in blood vessels. In such treatments, stents reinforce blood vessels and prevent restenosis following angioplasty in the vascular system.
Stents are relatively small, as they are often required to be passed through tight confines of anatomical lumens. A stent must often have great longitudinal flexibility to allow it to pass through tortuous curves of anatomical lumens. Stents typically comprise a fine network of struts which form a tubular scaffold. The tubular scaffold must often be capable of being crimped onto a delivery device, such as a balloon, to reduce its size to allow passage through anatomical lumens, and then forcibly expanded by the balloon to an enlarged, deployed state at the desired location within the body. For some stents, the tubular scaffold must be capable of self-expanding from its crimped state at the desired location within the body. After implantation and deployment, the tubular scaffold must have sufficient strength to support surrounding anatomical structures. Thus it will be appreciated that stents present unique design challenges.
Stents have in the past been made of metals, such as nickel-titanium alloys having shape memory and superelastic properties. The advent of polymer stents have presented further design challenges. The design of a polymer stent must take into account that, as compared to metal stents of the same dimensions, polymer stents typically have less radial strength and rigidity and less fracture toughness. Thus, there is a continuing need for a method and system for manufacturing polymer stents that (a) increase uniformity from stent to stent, (b) allow for tight control of design parameters, such as the thickness and dimension of individual stent struts, and/or (c) increase manufacturing efficiency.